1. With each bloom of the park’s cherry trees in April come creepy-crawlies to devour their leaves.

2. You’ve probably seen the caterpillars’ gray-white webs in the crooks of branches—nests from which to defoliate the canopy above.

3. Migrating songbirds such as the rare sky-blue warbler arrive at the same time—and feed on the insects. (Notable bird lover and novelist Jonathan Franzen made the warbler famous by using it as a main plot point in his book Freedom.)